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Per §4.13, pozzolana is best characterised (per IS 3812 Part II 1981) as a material that:
A{'text': 'Has high cementitious value on its own and replaces a fixed share of the cement directly', 'label': 'A'}
B{'text': 'Is a coarse inert filler that occupies the voids without entering the hydration reaction', 'label': 'B'}
C{'text': 'Has little cementitious value alone but reacts with Ca(OH)2 once finely divided and moist', 'label': 'C'}
D{'text': 'Is purely an air-entraining agent that has no chemical reactivity with cement hydrates', 'label': 'D'}
Answer & Solution
Correct answer: C. {'text': 'Has little cementitious value alone but reacts with Ca(OH)2 once finely divided and moist', 'label': 'C'}
1. §4.13 cites IS 3812 (Pt II) 1981: pozzolana is 'a siliceous or siliceous and aluminous material which in itself possesses little or no cementitious value but will, in finely divided form and in the presence of moisture, chemically react with calcium hydroxide at ordinary temperatures to form compounds possessing cementitious properties.'
2. Natural examples are volcanic ash, pumicite, opaline shales and diatomaceous earth; artificial examples are PFA / fly ash and burnt clay.
_Source: IGNOU ET-522 Block-1 Unit-4 Admixtures, §4.13, pp. 54-55_
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